Fuze signal processing circuit

ABSTRACT

1. In a fuze processing circuit which is not influenced by a high degree of modulation present in the target envelope signal, the combination comprising: A. A SOURCE OF TARGET ENVELOPE NEGATIVE SIGNALS HAVING A HIGH DEGREE OF MODULATION, B. A STORAGE CAPACITOR, C. A DIODE COUPLING ONLY THE NEGATIVE GOING PORTION AND BLOCKING THE POSITIVE GOING PORTIONS OF SAID TARGET ENVELOPE SIGNAL TO SAID STORAGE CAPACITOR, D. AN OUTPUT TERMINAL, E. A NORMALLY NON-CONDUCTING SILICON CONTROLLED RECTIFIER, F. SAID SILICON CONTROLLED RECTIFIER BEING SERIALLY CONNECTED ACROSS SAID STORAGE CAPACITOR, G. CIRCUIT MEANS COUPLING THE ANODE OF SAID SILICON CONTROLLED RECTIFIER TO SAID OUTPUT TERMINAL, H. CIRCUIT MEANS INCLUDING A Zener diode coupled to said source of target envelope negative signals and to the control electrode of said normally non-conducting silicon controlled rectifier for switching said normally non-conducting silicon controlled rectifier to a conducting condition to discharge said storage capacitor in response to the termination of a target envelope negative signal.

Dick et al.

Oct. 7, 1975 FUZE SIGNAL PROCESSING CIRCUIT [75] Inventors: John Dick, Riverside; John C.

Billings, Jr., La Sierra, both of Calif.

[73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: May 27, 1964 [21] Appl. No.: 370,740

[52] .U.S. Cl. l02/70.2 P [51] Int. Cl. F42C 13/00 [58] Field of Search 102/702, 70.2 P; 307/885; 323/22 Z [56] References Cited UNITED STATES PATENTS 3,022,732 2/1962 Paley 102/702 P 3,173,077 3/1965 Kirk et a1. 323/22 Z 3,198,989 8/1965 Mahoney..... 307/885 3,236,239 2/1966 Berkovits..... 307/885 3,237,023 2/1966 Wilhelm 324/111 Primary Examiner-Samuel Feinberg Assistant Examiner-C. T. Jordan Attorney, Agent, or FirmRichard S. Sciascia; Joseph M. St.Amand; T. M. Phillips EXEMPLARY CLAIM 1. In a fuze processing circuit which is not influenced by a high degree of modulation present in the target envelope signal, the combination comprising:

a source of target envelope negative signals having a high degree of modulation,

a storage capacitor,

a diode coupling only the negative going portion and blocking the positive going portions of said target envelope signal to said storage capacitor,

. an output terminal,

. a normally non-conducting silicon controlled rectifier,

. said silicon controlled rectifier being serially connected across said storage capacitor,

. circuit means coupling the anode of said silicon controlled rectifier to said output terminal,

. circuit means including a Zener diode coupled to 1 Claim, 4 Drawing Figures US. Patem Oct. 7,1975 3,910,192

JOHN D. DICK JOHN C. BILLINGS JR.

INVENTORS ATTORNEYS FUZE SIGNAL PROCESSING CIRCUIT The invention herein described may be, manufactured and used by or for the Government of the United States of America forgovernm ental purposes without the payment of any royalties thereon or therefor.

The present invention relates to that portion of a passive infrared actuated type fuzing system that processes the intercepted signal and makes the decision as to the correct time to actuate the firing of the missile warhead.

In the past it has been assumed that the signal shape in general is that of a sawtooth or exponentially increasing voltage waveform. The termination of the waveform (as the detector passes the jet engine tailpipe) is a sharply decreasing fall off to zero as the IR source seen by the detector disappears from the detector field of view. Prior circuitry has simply differentiated this waveform by means of a resistor-capacitor coupling network to select the sharp voltage transition occurring at intercept.

It has recently been determined that the target envelope as seen by the detector may not be the clean waveform as previously assumed. Recent tests have disclosed the fact that the target envelope of the jet engine exhaust plume may contain a high degree of modulation (up to 40 percent).

Due to the wide dynamic range required in fuzing systems, the magnitude of the modulation spikes described above may be much larger than the minimum signal necessary to produce fuze actuation. In addition, due to the wide range of intercept velocities and signal pulse width, there is no way in which the signal processing circuitry can distinguish between a true signal and the above modulation. The result of this is that the fuze may fire prematurely upon the modulation and thus fail to destroy the intended target.

Prior fuzing systems utilize the trailing edge of the intercept signal waveform as a timing reference point for detonating the missile warhead. The trailing edge of the signal is located by differentiation of the intercept signal in a resistor-capacitor coupling network.

An object of the present invention is to provide a fuze signal processing circuit which is not influenced by the high degree of modulation present in the target envelope signal as a result of the jet engine exhaust plume.

Another object of the invention is the provision of a fuze signal processing circuit that assures a more precise point of firing of the fuze by accurately detennining the exact point of signal fall off.

A further object is to provide a fuze signal processing circuit that minimizes the probability of dudding due to long pulse width signals obtained during slow-missileto-target overtake velocities.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 shows a schematic diagram of a preferred embodimcnt of the processing circuit.

FIG. 2 shows a modification of the circuit of FIG. 1.

FIG. 3 shows a further modification of the circuit of FIG. 1.

FIG. 4 shows graphically the point of firing of the circuit of FIG. 1.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several illustrations, there is shown in FIG. 1 the final amplifier stage 10- of an IR fuzing system (not shown) which provides the signal Wavefrom A; Because of the large modulation or'serrations present in Waveform A, a resistor-capacitor differentiating circuit would produce a premature pulse which would fire the fuze.

Waveform signal A is coupled through coupling capacitor 12 and diode 14 to charge capacitor 16 with a voltage as illustrated by Waveform C. Diode 14 is polarized so that a negative going signal is passed by the forward conductance of diode 14 but positive signals are blocked, thus, storing the negative peaks of Waveform A in capacitor 16. At the termination of the intercept Waveform A, the peak amplitude of the signal is stored in capacitor 16 and held by choosing the values of capacitor 16 and resistor 18 to have long time constant.

Waveform signal A is also coupled through coupling capacitor 20, with a small amount of integration as shown by Waveform B, and Zener Diode 22 to the control electrode of silicon controlled rectifier 24. As shown in FIG. 4, there is no voltage difference across Diode 22 so that it does not conduct. At the termination of the signal (Waveform A) as the IR source as seen by the IR detector passes from the detector field of view, Waveform B drops to zero, the voltage across Diode 22 increases until its breakdown voltage (V FIG. 4) is exceeded and it begins to conduct. This diode current is applied to the control electrode of controlled rectifier 24 and causes it to switch, thereby discharging capacitor 16 and producing a precise trigger pulse at terminal 28 to mark the termination of the detected signal. The portion 30 of Waveform C is the nor mal decay of resistor 18 and capacitor 16 time constant while the portion 32 shows the discharge when controlled rectifier 24 is switched on.

FIG. 2 is functionally the same as FIG. 1 but has been modified by replacing the dual coupling capacitors 12 and 20 with a single coupling capacitor 36.

FIG. 3 is functionally the same as FIG. 1 with the ad dition of diode 38 and integrating capacitor 40 to prevent narrow spikes from inadvertently firing rectifier 24.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a fuze processing circuit which is not influenced by a high degree of modulation present in the target envelope signal, the combination comprising:

a. a source of target envelope negative signals having a high degree of modulation,

b. a storage capacitor,

c. a diode coupling only the negative going portion and blocking the positive going portions of said target envelope signal to said storage capacitor,

d. an output terminal,

e. a normally non-conducting silicon controlled rectifier,

f. said silicon controlled rectifier being serially connected across said storage capacitor,

g. circuit means coupling the anode of said silicon controlled rectifier to said output terminal,

rectifier to a conducting condition to discharge said storage capacitor in response to the termination of a target envelope negative signal. 

1. In a fuze processing circuit which is not influenced by a high degree of modulation present in the target envelope signal, the combination comprising: a. a source of target envelope negative signals having a high degree of modulation, b. a storage Capacitor, c. a diode coupling only the negative going portion and blocking the positive going portions of said target envelope signal to said storage capacitor, d. an output terminal, e. a normally non-conducting silicon controlled rectifier, f. said silicon controlled rectifier being serially connected across said storage capacitor, g. circuit means coupling the anode of said silicon controlled rectifier to said output terminal, h. circuit means including a Zener diode coupled to said source of target envelope negative signals and to the control electrode of said normally non-conducting silicon controlled rectifier for switching said normally non-conducting silicon controlled rectifier to a conducting condition to discharge said storage capacitor in response to the termination of a target envelope negative signal. 